This was because I wanted a sentence on my about page that would read: "This blog has 8,586 posts, 2,353 comments, 5,936 embedded images, and 3,258 outbound links." https://artlung.com/about/ -- I use a cron to run the CLI prefixed files to update the outbound links and images. For your use, possibly.

cli-update-image-count.php

<?php

$current_dir = dirname(__FILE__);
// load wordpress functions
require_once( $current_dir . '/../../../wp-load.php');

$meta_key = 'post_image_count';

// TODO
// TODO post_link_count

// get posts without the post_word_count key
$args = [
	// type post
	'post_type' => ['post', 'page'],
	'posts_per_page' => 200,
	'post_status' => 'publish',
	'orderby' => 'date',
	'order' => 'ASC',
	'meta_query' => [
		[
			'key' => $meta_key,
			'compare' => 'NOT EXISTS',
		],
	],
];

// https://developer.wordpress.org/reference/functions/get_posts/
$posts = get_posts($args);
foreach ($posts as $post) {
	// get the finalized content
	$content = get_the_content();
	// parse the content for img tags
	$dom = new RoanokeDOMDocument();
	$dom->loadHTML($content);
	$images = $dom->getElementsByTagName('img');
	$image_count = $images->length;
	$meta_value = $image_count;

	// if already has key, continue
	if (get_post_meta($post->ID, $meta_key, true)) {
		printf("Post %s already has meta key %s\n", $post->ID, $meta_key);
		continue;
	}
	printf("DONE: Post %s meta key %s will be set to %s\n", $post->ID, $meta_key, $meta_value);
	update_post_meta($post->ID, $meta_key, $meta_value);

}

cli-update-link-count.php

<?php

$current_dir = dirname(__FILE__);
// load wordpress functions
require_once( $current_dir . '/../../../wp-load.php');

$meta_key = 'post_link_count';

// TODO
// TODO post_link_count

// get posts without the post_word_count key
$args = [
	// type post
	'post_type' => ['post', 'page'],
	'posts_per_page' => 200,
	'post_status' => 'publish',
	'orderby' => 'date',
	'order' => 'ASC',
	'meta_query' => [
		[
			'key' => $meta_key,
			'compare' => 'NOT EXISTS',
		],
	],
];

// https://developer.wordpress.org/reference/functions/get_posts/

$posts = get_posts($args);
foreach ($posts as $post) {
	// get the finalized content
	$content = get_the_content();
	// parse the content for img tags
	$dom = new RoanokeDOMDocument();
	$dom->loadHTML($content);
	$aTags = $dom->getElementsByTagName('a');
	$links = [];
	foreach ($aTags as $anchor) {
		$href = $anchor->getAttribute('href');
		$is_this_to_artlung_com = false;
		if (strpos($href, 'http') === 0) {
			$domain_of_link = parse_url($href, PHP_URL_HOST);
			if ($domain_of_link == 'artlung.com') {
				$is_this_to_artlung_com = true;
			}
			if ($is_this_to_artlung_com) {
				$links[] = $href;
			}
		}
	}
	// array_unique
	$links = array_unique($links);
	$link_count = count($links);
	$meta_value = $link_count;

	// if already has key, continue
	if (get_post_meta($post->ID, $meta_key, true)) {
		printf("Post %s already has meta key %s\n", $post->ID, $meta_key);
		continue;
	}
	printf("DONE: Post %s meta key %s will be set to %s\n", $post->ID, $meta_key, $meta_value);
	update_post_meta($post->ID, $meta_key, $meta_value);

}

functions.php

add_shortcode('post_stats_sentence', function() {
	return Roanoke::postStatsSentence();
});

Roanoke.php

<?php

/**
 * class Roanoke
 */
class Roanoke {
  
    // Note, this depends on every post having a post_image_count and post_link_count
  	public static function postStatsSentence() {
        $number_of_published_posts = wp_count_posts()->publish;
        $number_of_published_comments = wp_count_comments()->approved;
        $number_of_embedded_images = self::totalMetaValue('post_image_count');
        $number_of_outbound_links = self::totalMetaValue('post_link_count');

        $number_of_published_posts = number_format($number_of_published_posts);
        $number_of_published_comments = number_format($number_of_published_comments);
        $number_of_embedded_images = number_format($number_of_embedded_images);
        $number_of_outbound_links = number_format($number_of_outbound_links);

        $sentence = sprintf('This blog has %s posts, %s comments, %s embedded images, and %s outbound links.',
            $number_of_published_posts,
            $number_of_published_comments,
            $number_of_embedded_images,
            $number_of_outbound_links
        );
        return $sentence;
	}
  
  	private static function totalMetaValue( string $string ) {
        global $wpdb;
        $sql = "SELECT SUM(meta_value) FROM {$wpdb->prefix}postmeta WHERE meta_key = '{$string}'";
        $result = $wpdb->get_var($sql);
        return $result;
	}
}

RoanokeDOMDocument.php

<?php
class RoanokeDOMDocument extends DOMDocument
{
	/**
	 * When specifying we want to to be sure the output does not contain the doctype, html, or body tags.
	 * @param $source
	 * @param $options
	 *
	 * @return void
	 */
	function loadHTML( $source, $options = 0 ) {
	// https://stackoverflow.com/questions/4879946/how-to-savehtml-of-domdocument-without-html-wrapper
		$options = $options ?: LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD;
		parent::loadHTML( $source, $options );
	}

}